1. Field of the Invention
The present invention relates to fuel transfer from a plurality of fuel tanks to the engine of a vehicle, and more particularly, to a method and apparatus for maintaining substantially equivalent fuel levels within the plurality of fuel tanks and for ensuring that no fuel is spilled in case of any malfunction of the transfer apparatus.
2. Description of the Related Art
Vehicles such as, for example, heavy and medium duty trucks many times employ a dual fuel tank configuration providing a large fuel capacity. A fuel pump is utilized to draw fuel from the fuel tanks to the vehicle engine.
As is known in the art of internal combustion powered vehicles, fuel pumps remove more fuel from fuel tanks than is utilized in the engine so as to cool the fuel injector pump while supplying sufficient pressure to the fuel injectors. The surplus fuel which is not used by the engine is constantly returned to the fuel tank. In the dual tank configurations currently utilized, fuel is drawn from and returned to both fuel tanks simultaneously. These systems do not draw fuel evenly from both tanks nor do they return fuel evenly to both tanks. Uneven fuel draw and return can be attributed to many factors affecting fluid flow, including pressure differentials and physical attributes of the fluid distribution system including, but not limited to partial blockage of distribution piping. Spillage may occur if fuel is drawn primarily from one of the two tanks and fuel is returned primarily to the other of the two tanks.
Roads and parking areas are generally formed with a crowned configuration leading to one of the two fuel tanks being lower relative to the other. Fuel is more easily drawn from the higher tank and consequently the lower tank has less fuel drawn from it. This can exacerbate the problem of uneven fuel draw and the consequent spillage which can occur.
Uneven fuel draw and return additionally causes balance problems when one of the two fuel tanks contains significantly more fuel than the other. Hydrocarbon fuel typically weighs approximately 6 lbs. per gallon and the fuel tanks in question generally have a capacity of approximately 100 gallons. The substantial weight differential caused by an uneven amount of fuel in the two tanks can cause maintenance and other problems for the vehicle operator including, for example, uneven tire wear. An additional problem associated with the dual tank configuration occurs when one of the two tanks is emptied and air is drawn into the engine from the fuel supply line connected to the empty tank. When air is drawn into the engine, engine stall is experienced and restarting the engine is problematic.
Many vehicles utilize an engine driven fuel pump to transfer fuel from the fuel tank to the engine. As is known in the art, the output of an engine driven fuel pump is a linear function of its speed. Therefore, during engine crank, when engine speed is very low, engine driven fuel pumps create only a small amount of lift and, consequently, relatively small flow. With this in mind, engine driven fuel pumps are slow to prime. A discrete priming pump would allow for faster priming of an engine driven fuel pump. A priming pump will be particularly advantageous, for example, if the engine has run out of fuel, the fuel supply line is completely emptied by drain back occurring when the engine is not running, or a filter change has been effected. For example, during fuel filter change, the new fuel filter must be filled with fuel to complete the fuel filter change and a priming pump may be utilized to provide fuel to the newly installed fuel filter and to prime the engine driven fuel pump.
Modern vehicles conventionally utilize computer control systems to monitor and control various vehicle systems. Vehicle computer control systems typically utilize three stages: input, processing, and output. The input stage of a vehicle control system receives input from various sensors placed throughout the vehicle to monitor vehicle conditions. The processing stage of a computer control system compares the various inputs to the acceptable operational parameters stored within the memory of the computer control system. Finally, the output from a vehicle""s control system signals changes in vehicle operation to bring the input parameters within the desired ranges or values. A typical vehicle control system, or electronic control module (ECM) includes various inputs and outputs. Various sensors throughout the vehicle monitor the operational parameters of the vehicle and transmit these operational parameters to the ECM, e.g., in the form of an electrical signal. Generally, the three main functions of the ECM, i.e., input, processing, and output, are performed by various sections of the ECM. For example, the input stage of the ECM is performed by an input section operable to convert signals from the various vehicle sensors into a form the ECM can effectively utilize. The processing section of the ECM generally includes a memory section having data stores indicating acceptable and/or optimum operational parameters. The processing section of the ECM generally also includes a logic section for performing necessary arithmetic calculations including comparisons of sensor inputs to acceptable parameters stored in the memory section. Furthermore, the arithmetic calculations of the logic section may be utilized to convert sensor signals into alternative forms. For example, the input to the ECM from an engine speed sensor (for example, sensing rotations of the various parts of the car""s transmission) can be transformed via the logic section of the ECM into a measure of vehicle speed which can then be output via the ECM output section to, e.g., the vehicle speedometer. Furthermore, many vehicles utilize additional microprocessors placed throughout the vehicle to control various vehicle functions.
In the above-identified patent application Ser. No. 09/893,940, a fuel transfer apparatus was disclosed including a pair of fuel tanks and a transfer pump positioned to transfer fuel between the two tanks. Fuel was provided to an engine from a first one of the two fuel tanks. Excess fuel was returned to a first one of the two fuel tanks. When the level in the first fuel tank was less than the level in the second fuel tank by a predetermined amount, the transfer pump transferred an amount of fuel from the second fuel tank to the first fuel tank. Fuel level sensors were utilized to monitor the level of fuel in the two fuel tanks and to provide inputs to a microprocessor which controlled the transfer pump.
One of the problems which could occur with such structure was that, due to system malfunction, the transfer pump could possibly continue to pump, even though the fuel levels were such that no further transfer was called for. Such malfunctions could be due to a number of reasons such as, for instance, a sender unit which xe2x80x9csticksxe2x80x9d at empty or a pump switch which sticks in the xe2x80x9conxe2x80x9d position. This condition could result in overfilling the main tank and resulting in a pressurized tank. When the fill cap is removed, the tank returns to its original shape, resulting in fuel being spilled and potential fuel leakage to the ground by the rollover valve vent line.
What is needed in the art is an apparatus for effectively providing fuel from a dual fuel tank configuration to an engine while maintaining a substantially equivalent volume of fuel in each of the fuel tanks, while preventing overfilling of a tank.
What is further needed in the art is an apparatus for maintaining a substantially equivalent volume of fuel in a plurality of fuel tanks, which apparatus may be configured to include an integral controller or which may utilize the existing vehicle ECM, and preventing overfilling of a tank.
What is further needed in the art is an apparatus which advantageously combines a device for maintaining a substantially equivalent level of fuel in a dual fuel tank configuration while also providing a priming pump for the engine mounted fuel pump of a vehicle, and a means to guard against overfilling of a tank.
The present invention is directed to improve upon the aforementioned fuel storage and distribution systems for vehicles having more than one fuel tank, wherein it is desired to utilize a dual fuel tank configuration in which the fuel levels in both fuel tanks remain substantially equal. The present invention provides an electric transfer pump configured to be in fluid communication with both fuel tanks. Fluid level sensors measure the fluid level in both fuel tanks and are communicatively connected to the electric transfer pump via a microprocessor. When the fluid level in one of the tanks reaches a predetermined lower level than in the other tank, the microprocessor signals the electric transfer pump to distribute fuel from the tank having the greater fuel volume to the other tank.
The microprocessor utilized in accordance with the present invention may be a stand-alone microprocessor mounted externally of the electric transfer pump, may be incorporated into the pump itself, or may comprise the vehicle ECM. Utilizing the existing vehicle ECM can be beneficial from a cost standpoint, since modern vehicles are conventionally equipped with an ECM and, therefore, an additional microprocessor is not required. However, installations utilizing a stand-alone microprocessor, or a microprocessor incorporated into the electric transfer pump may be advantageous in a retrofit situation, or in a vehicle having an ECM without an available input, or without the additional memory required to operate the electric transfer pump.
In one form of the current invention, the first of the two fuel tanks is in direct fluid communication with the engine whereby fuel is supplied to the engine from the first tank and excess fuel returning from the engine is returned to the first tank. Fuel level sensors are operatively connected to both fuel tanks. Fluid level measurements from the two fuel level sensors are communicated to a microprocessor (for the purposes of this document, xe2x80x9cmicroprocessorxe2x80x9d is meant to encompass any of the computational/control devices known in the art) which evaluates the two fuel level signals and determines whether fuel should be transferred from the second fuel tank to the first fuel tank. Fuel is transferred when the fuel level in the first fuel tank reaches a predetermined lower level than the fuel level in the second fuel tank.
To prevent the transfer pump from overfilling the main tank due to malfunction of the system, an overfill line is provided for connecting the tops of the two tanks. Thus, the two tanks will not be pressurized because the connecting line will prevent the pressurization of the tanks. The line extends above the two tanks so that, absent pressure in the main tank, no fuel will flow through the line. However, if pressure is present in the main tank and if the main tank is full, fuel will flow through the line to the other tank. Thus, the line acts as a pressure equalizer between the two tanks and also as a transfer device for transferring fuel from the overfilled main tank to the less full other tank.
In a further embodiment of the present invention, a three-way valve is positioned intermediate the transfer pump and the primary fuel tank. The three-way valve includes an inlet for receiving fuel from the transfer pump and a pair of outlets. A first one of the outlets is connected to the primary fuel tank and a second one of the outlets is connected to a fuel supply line connecting the primary fuel tank and the vehicle engine. In this embodiment, the transfer pump may advantageously be utilized to prime an engine-driven fuel pump utilized to transfer fuel from the primary fuel tank to the engine. To prime the engine driven fuel pump, the first outlet on the three-way valve is closed and the second outlet is opened, so that the transfer pump can be energized to provide fuel to the fuel supply line and thereby prime the engine-driven fuel pump. This priming feature can, e.g., be utilized at engine start or after a fuel filter change. After priming, the second outlet of the three-way valve is closed and the first outlet is opened so that the transfer pump can transfer fuel between the two fuel tanks.
An advantage of the present invention is the ability to prevent fuel spillage in a vehicle having multiple fuel tanks by eliminating the possibility that more fuel is returned to a fuel tank than is taken from the fuel tank.
Another advantage of the present invention is the ability to maintain substantially equal fuel volumes within a multiple fuel tank configuration and thus eliminate balance problems associated with unequal fuel volumes.
A further advantage of the present invention is the ability to eliminate engine stall occurring as a result of air being drawn from an empty fuel tank.
Yet another advantage of the present invention is the ability to provide an apparatus for maintaining a substantially equivalent volume of fuel in a plurality of fuel tanks, which apparatus may be configured to include an integral controller or which may utilize the existing vehicle ECM.
Yet a further advantage of the present invention is the ability to combine a device for maintaining a substantially equivalent level of fuel in a dual fuel tank configuration while also providing a priming pump for the engine mounted fuel pump of a vehicle.
Still a further advantage of the present invention is the provision of an equalizing line to ensure that, if the system malfunctions, fuel is returned from the overfilled main fuel tank to the less full tank.